Electrical measuring instrument.



PATENTED APR. 30, 1907.

A. 0. BBNEGKB. ELECTRICAL MEASURING INSTRUMENT.. APPLIOATION TILED SEPT. 19, 1902. RENEWED APR. 1, 1907.

ADELBERT O. BENECKE, VAILSEURG, NEW JERSEY.

ELECTRICAL MEASURING INSTRUMENT.

Specification of Letters Patent.

Patented April' 30, 1907.

Application filed September 19, 1902. Renewed April 1, 1907. Serial No. 366.861.

T 0/ whom, it may concern.-

Be it known that I, ADELBERT 0. BEN- ECKE, a subject of the German Emperor, residing at Vailsburg, county of Essex, and State of New Jersey, have made a new and useful Invention in Electrical Measuring Instruments, of which the following is a specification.

My invention is directed particularly to an improvement in dampening devices for the movable parts of such instruments, for the purpose of effecting a dead beat action upon the index needle or pointer when the instrument is 'connected in circuit with a source of electrical energy, and to this end it consists in the structural apparatus hereinafter described and illustrated in the accompanying drawings, the especial points of novelty being particularly pointed out in the claims at the end of the specification.

For a full and clear understanding of the improvement such as will enable others skilled in theart to construct and apply the same to electrical measuring instruments, reference is had to the drawings, in which,

Figure 1 represents a sectional view taken through the top of the casing of an instrument illustrating my improvement as attached'to the movable or rotary part thereof, the movable coil, its supporting pivots and the sustaining pillars or posts for the movement being shown in elevational view. Fig. 2 is a plan view of Fig. l as seen looking thereat from the bottom toward the top of the drawings, the lower cover or cap being removed for the purpose of showing the internal structure of my improvement. Fig. 3 s an enlarged sectional view taken through that portion of the instrument embodying my improvement, and on the line xx Fig. 2, and as seen looking thereat from the top toward the bottom of the drawings, the retarding vanes and attached parts of the movement however, not being shown in this view. Fig. 4 is a perspective view illustrating the. retarding vanes attached to the rotary or movable partof the instrument. Fig. 5 is a sectional view taken through that por tion of the instrument embodying my im provement, and on the broken line l g Fig. 2 and asseen looking thereat from left to right in the direction of the arrows, a part of the movable coil being also shown. Fig. 6 is a plan view of the two part cover or cap which incloses the retarding vanes in the double or duplex air chamber.

In the use of electrical measuring instruments, when the instrument is connected in circuit with a source of electrical energy for the purpose of obtaining definite indications as to current quantity, current ressure, or the amount of energy being absorbed, it is important that the indicating needle be renderec dead beat in its action so as to give an instantaneous indication of the factor it is sought to obtain. Prior to my invention various types of dampers were devised for effecting this result, some of which are made dependent upon magnetic influences between the rotary coil of the instrument and the field magnets thereof, such for instance as are utilized in the well known Vfeston instruments in which the coil is wound upon a light spool of aluminium, the inductive effect of the current and the permanent magnetic field in such instruments tending to cause such dead-beat action. Such instruments, however, are not adapted to give the best results when used in connection with alternating currents for reasons well understood by those skilled in the art. In Incasuringinstruments adapted for use in connection with such currents it therefore becomes necessary to depend upon other devices for effecting the dead beat result. Recognizing this fact, therefore, inventors have heretofore at.

tempted to produce a dead-beat action in such instruments, by one or more vanes or fans carried by the index needle or pointer and exerting a dampening or retarding influence by displacing the air within the easing of the instrument. To effect any substantial dead-beat action with such a dampening device, however, a vane or fan of relatively large area and hence of considerable mass is required which necessarily increases the momentum of the moving aart and, therefore, materially affects the accuracy of the indications of the instrument. Instruments have also been constructed prior to my invention in which the retarding or damening influence is effected by a curved dashpot secured within the casing and a hollow or tubular curved plunger carried at one end of the needle, as disclosed in British Patent No. 12,074 granted July 4th, 1900 to Siemens Bros. Company, Ltd. Such an instrument, however, requires one or more counterweights for counterbalancing the weight of the plunger carried by the needle. An instrument made in accordance with the specification of British Patent No. 12,074 will,

too

owing to the peculiar construction of the dashpot, tend to give a fairly good deadbeat action, but owing to the masses of the parts carried by the movable part of the movement and the unsymmetrical location of said masses with relation to the axis of rotation there result elements of error which more than compensate for the dead-beat effect of the dash-pot, so that although the needle gives an approximate dead-beat indication the instrument has not given an actual indication of the true current reading. Still further attempts have been made more closely approximating my improvement in which two vanes or fans, or the equivalents thereof, are secured directly to the axis of the rotary index needle or pointer and are inclosed in a double or duplex surrounding chamber, as disclosed in U. S. Patent to Edward Weston No. 433,637, granted Aug. 5th, 1890, and U. S. Patent to Kennally No. 500,236, granted June 27th, 1893. A further attempt has been made in this direction also, as disclosed in U. S. Patent to Knowles No. 520,964, of June 5th, 1894. None of these devices, however, disclosed in th.eabove named patents are adapted to produce an absolute dead-beat effect under the best possible conditions. The invention disclosed in British Patent No. 12,074 above referred to approaches nearer to such a result.

111 the construction of an electrical measuring instrument, so that it may give the best results as to the actual measurement of the current flowing through the operative coil or coils, it is important that the needle shall settle at the limit of its throw or range at the instant that it is connected in circuit with a source of electrical energy, and that it shall thereafter give instantaneous deadbeat indications of any change whatever of current flow. To effect this, therefore, it is especially essential, first, that the mass of the combined moving parts of the movement shall be relatively small; second, that the mass of the dampening device carried by the moving part of the movement shall be symmetrically disposed with relation to the axis of rotation of said part so as to thereby avoid the use of any counter-balances whatever; third, that the mass of the dampening device shall be as near the center of rotation of the movable part as possible; and, fourth, that the mass of the dampening device, when designed so as to displace a volume of air, shall be so shaped and arranged as to cause a maximum displacement thereof with a relatively low rate of flow.

In constructing a retarding device embodying the essential principles of my invention it is also important that the clearance between the lateral edges of the vanes or fans and the interior walls of the air chambers be such that there shall be no possibility of any mechanical contact between the vanes and said. walls. If the areas of the vanes and the interior diameters of the duplex air eha1nbers are large the clearance may be relatively large and the turned out edges of the VZUMH may be correspondingly diminished, or even done away with. But, as before pointed out, to increase the areas of the vanes is to increase the momentum of the moving parts and to decrease the same, unless the edges be turned outward in opposite direct M15. is to increase the air flow to such an extent that when said vanes assume a practical size a device is produced which does not effect a dead-beat action. I have ascertained by a long series of carefully conducted experiments that practical results of a d rad-beat nature with such a device can only be obtained when the area of the vanes and the diameters of the combined air chambers are relatively small, the vanes being so constructed that the outflow of air is small eonipared to the volume of air acted. upon by them and the confining air chamlmrs. ln other words, with a safe clearance the area of the vanes and the volume of the air chainbers being small the depths of the cups or the depths of their out-turned edges will determine the perfect acting retarding device. I have obtained most excellent results will] a device connected in accordance with l i;,1;. 1, 2, 3 and 4 and upon the scale therein in.i1- cated, said figures having been mate directly from a working damper and applied to a Weston instrument of the alternating current type. My improvement embraces all of these essential qualifications.

Referring now to the drawings in detail and first to Fig. l, 1 represents that part of the casing of an electrical measuring instrument which supports the movemei'it enibracing the rotary coil, index needle and interconnected parts removable therefrom as a unit. 2 represents the rotary or movable coil and 3, S, the pivots therefor, said pivots being attached directly to the coil and supplied with the usual jewel bearings 4:, 1, ear ried by bridges 5, 5, secured at their opposite ends to supporting pillars or posts (5, (i, the usual coiled springs or springs electrically connected with the coil being shown; said parts as described. so far constituting what is known as the movement and being not substantially different from the like parts found in the well known l Veston electrical measuring instruments described and shown in numerous U. S. patents heretofore granted to Edward Weston, of Newark, N. J

The usual field magnet coils or permanent magnets, as the case may be, are not shown, for the reason that their application. is at once obvious, my improvement being, as above indicated, directed solely to novel means for effecting a dead heat action lCO upon the index needle carried or supported by the rotary or movable element illustrated in Fig. 2 of the drawings.

My improvement embodies a double or duplex air chamber 10, 10 constructed preferably of a cylindrical outer metallic part 7 and an interior or concentric structure 8 (partly cylindrical and partly approximately elliptical) the outer or approximately elliptical ends being brazed or soldered at 9, 9, to the inner wall of the part 7, so that the two air chambers 10, 10 are located on opposite sides, the elliptical ends being such that they will permit of the insertion of the free ends of the sustaining pillars or posts 6, 6, and the lower bridge 5 into the inner concentric chamber and in the position shown in Figs. 1, 2 and 5.

11, 11 are short cross-bars brazed or otherwise secured to the inner surfaces of the elliptical ends and 12, 12 screws passing upward through said cross-bars and into the lower bridge 5, such an arrangement making my improvement readily applicable to the well known Weston electrical instruments as they are at present being placed upon the market.

Referring now to Fig. 4, 20 represents a thin disk, 19, 19 arms and 18, 18 vanes or fans, said parts being all stamped or formed in one thin inte ral piece from aluminium with the lateral edges of the two vanes turned outward in opposite directions to form forwardly directed marginal flanges, as shown. These parts constitute a double or duplex vane or fan attached directly to the lower pivot 3 which supports the movable coil 2 and the structural arrangement is such that when the vanes are in position within the individual compartments of the duplex air chamber 10, 10, the disk 20 will fit, without frictional contact, in a slotted opening 17 (see Fig. 3) between the upper edge of the inner part of the chamber and the cover 14 therefor, said cover being constructed in two parts, as clearly shown in Fig. 6, and so de vised that when the parts are put together there are three openings, 15, 15 and 16for the pillars or posts 6, 6, and the pivot 3. 13 is a bottom cap for the lower end of the duplex air chamber, said cap being made pref erably of non conducting material, as hard rubber, for the purpose of avoiding the evil effects of Foucault currents.

The parts are assembled as follows-The delicate vanes or fans 18, 18 with their sustaining arms 19, 19 and disk 20 are secured directly to the lower pivot 3 and the coil and attached parts are placed in the position shown in big. 1, after which the lower bridge 5 is secured in place in the usual manner with the lower pivot resting upon its jewel bearing 4. The duplex air chamber is then placed in position with the elliptical ends of the inner part 8 siu'rounding the ends of the lower bridge. The screws 12, 1.2 are then passed through holes in the cross-bars 11 and secured directly to the-bridge 5. The two parts of the cover 14 are then slipped into position in a'groove in the upper face of the outer cylindrical part 7, being held therein very much in the same manner that a watch or stal is held by the bezel thereof. The lower cap 13 is then secured in position and the entire movement is ready to be placed in the field of the energizing coils or magnets not shown, but well understood.

It will be obvious on inspection of Figs. 1 3, 4 and 5 that inasmuch as the disk 20 practically closes the entire slotted opening 17 between the upper edge of the cylindrical portion of the inner part 8 and the cover 14, the duplex air chambers 10, 1.0 will retain the air therein with the best possible effects, it being apparent that as the vanes are rotated in the direction of the arrows shown in Fig. 2 and inasmuch as the lateral edges thereof are turned outward in opposite directions so as to form cups, the best compressive or checking effects upon the confined air will at all times be had, so that no matter what may be the magnetizing effects upon the movable coil 2 the needle of the instrument will settle instantly when it reaches the extreme limit of the throw thereof.

My improvement embodying as it does the double or duplex air chamber with a double.

or duplex vane or fan located therein, the same being constructed of very light material such as aluminium and with the outer edges of both vanes turned inward and in opposite directions and relatively close to the inner walls of the chambers together with the light metal disk 20 closing the slotted opening 17, is such that when the needle and moving parts attached thereto are caused to move there will be a maximum displacement of air at all times with a relatively low rate of flow, so that the needle will always give an absolutely dead-beat effect, and this feature constitutes the essence of my invention. Although I have described my invention as having an especial adaptability for use in connection with alternating current electrical measuring instruments, I do not limit it to that type of instruments, as obviously it may be adapted to electrical measuring instruments generally, and my claims hereinafter made are designed to be of such scope as to include all such uses.

I believe it is broadly new with me to produce an air dampening device for use with instruments of precision having vibratory needles in which the dampening effect upon the needle is absolutely dead-beat, and is produced by so locating the parts of the damper, vane or fan that the momentum attributable to said damper, vane or fan is practically nil and to so construct and arrange the v2 ne or "fan Within the air chamber that it i.l always d'splace a maximum vel ume cl air with a relativelyloiv rate of flow tl'ieree'li', and my claims are to be construed gener'c in this particular, such a result, l ar as l m aware, never before having been accem, l ed prior to my invention.

llavin g thus descrilLed my invent ion vxhat I claim and desire to secure i /y Letters Patent of the Uni led Staies is- 1. A retarding device for the movable part of an electrical measuring instrume the same consisting of a duplex air ch amber and a two part vane or fan located therein, said vane or lian heing construcled with the lateral edges of each part thereof turned outward in opposite dire tions to form il ornardl v directed mar ginal flanges.

2. A retard] ng device For the movalrle part 0 an elcclrical measuring instrument, the same consisting of a double or duplex air chamber and a two-p art ro tator vane loca tel: therein, said vane heing sjfmmetricallv dispose l with relation to the location of the movable part and with. the lateral of each part of said vane turned outward in opposite directions to form forwardly dircied marginal ii an 3. in an electrical measuring instrument, the combination oi a movable part thereof with a retarding device for said movahie part, said device embracing an ai r chamber having a slotted opening and a vane or fan located in said chamher, said vane or fan heing at tached to said. movahlc part a disk which closes "the upper end of the air chamher and the slotted opening, so that the contaii ed air in the chamher is held in check when the vane is moved, suhrta liall v as descrihed.

4. In an. electrical measuring instrument, the comhinaiion of movable part thereof with a re ling device "for said movahlc p art, sai device emsracing i e vanes or l ans op disposed with relation to the axis of fans being located in an air chamher and. connected. to the movable part of "the ii'istrumcnt by a dish which holds the air in check when the vanes are moved, sulistantiall as described.

5. In an electrical measuring instrument, the comhiinil'ion. of a movable part tin of with a retarding device for said movable part, said device embracing an air chamimr; a vane or fan located therein. and. opera Lively connected to said. mova le part, and a rotatable dish ad ap'tcd to hold the air contained within the chamber in check when the vane is moved, substantially as descrihed.

6. An electrical measuring instrument pro said movahle part, each of said vanes or carers vided with a movahle part and supper-l ing posts or pillars therefor, in comhinarion v. i l h a retarding device dctachahly secured RU said posts or pillars, said device comprising a duplex air chamber, a duplex vane or fan seoured lo said movable part h v means ol :1 disk integral "with said ane or fan, ihe individual parts of said vane or lian laying inclosed in the individual comparimezns of said air chamber.

7. A retarding device for an rlrcrricrl measuring instrument cmhr: c ing an airchaniher and a vane or fan inclorcd =herrin, said vine or fan being provided wiih in) \vardly directed lnargiral large-s aid with means for connecling 1t lo the movriile pan of an electrical measuring insrrumem and the cross-section of the air chamher and ill! area of the vane heing relaiivel v such illill the outlloxv ol the air under prei-asure hen: the vane hears c supsianlialljv constani relation to the torque applied to the movade part of the instrument, suhstanfriall v as do scribed.

8. A retarding device for an elecirical measuring instrument having a roiar or mov: his part, said device consisting of an air. chamber, a vane located therein and ai l achrd to the rota. or movable part of die insirument, pillars srcured. to lhc hod r oi the instrunlent, bridges mounted. upon said pillars 'lor errring the roiar v or movable pan of the instrument and means for de'iacliaid v wouring said air chamner to one ol" said hridgrs.

S). An electrical measuring inslrulnmn provided v th. tno bridges or pivot .llfiliUI'ih 'n'hich carry the usual jewel hearings pillars or posts a ched directly to lh: casing for supporiing said hridges or pivot h ll'piml'mi in combination with a dampening device emhracing an air chamher and a vane inc for (iota-chant, securing said dampening device 2s a whole to one of said hridge--:, lllih stain ia as described.

10. A retarding devi e for electrical nun uring strumens, combined nil h a re i a L a i do part o'l said in:. ument said device ('(ll]1l)1'l ing an air chamber, a vane inclor-ri'l n iilllZ. said chamher and secured to suit iolanhle part to move thertm'iih, said vane hring pro vided with l'orvvardlv direcled marginal flanges.

ln iesiimony whereol I have signed m name to this speci'licz'tlion in the prcreuc'e cl tivo suhscrilying vri i nesses.

nDElqlllCll'l (l. lll iJ lit ii l lv lVi tnesses W. H. Yawca, Emv. F. lVEJ'roN. 

